The ruby sinatra app exposes two health endpoints:
/health/ready/health/live
By default these endpoints return 200 OK with a sample JSON body.
To simulate that the app in unhealthy, we can delete the files in /tmp:
/tmp/readyaffects API endpoint/health/ready/tmp/liveaffects API endpoint/health/live
/returns a simpleHello world\n(for curl and webbrowsers)/envreturns all environment variables as JSON
$ docker run -d --rm -p 9292:9292 docker.io/kicm/healthcheck-demoOpen your browser and play with the different endpoints:
- http://localhost:9292/
- http://localhost:9292/env
- http://localhost:9292/health/live
- http://localhost:9292/health/ready
apiVersion: apps/v1
kind: Deployment
metadata:
name: healthcheck-demo
spec:
replicas: 3
selector:
matchLabels:
app: healthcheck-demo
template:
metadata:
labels:
app: healthcheck-demo
spec:
containers:
- name: app
image: docker.io/kicm/healthcheck-demo
ports:
- containerPort: 9292
name: http
env:
- name: FOO
value: bar
- name: HELLO
value: world
livenessProbe:
httpGet:
port: http
path: /health/live
periodSeconds: 5
readinessProbe:
httpGet:
port: http
path: /health/ready
periodSeconds: 1Now you can play with these endpoints. Let's make one Pod "not ready":
$ kubectl exec -ti healthcheck-demo-745554966d-f9jvz bash
www-data@healthcheck-demo-745554966d-f9jvz:/$ rm /tmp/readyAfter 3 seconds you see that this Pod is not ready anymore (0/1 in column READY):
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
healthcheck-demo-745554966d-f9jvz 0/1 Running 0 4m45s
healthcheck-demo-745554966d-ghxqk 1/1 Running 0 4m39s
healthcheck-demo-745554966d-xwhp5 1/1 Running 0 4m42sLet's make it unhealthy now: delete the file /tmp/live inside the Pod:
$ kubectl exec -ti healthcheck-demo-745554966d-f9jvz bash
www-data@healthcheck-demo-745554966d-f9jvz:/$ rm /tmp/liveAfter around 15 seconds, Kubernetes will restart this Pod and everything is fine again:
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
healthcheck-demo-745554966d-f9jvz 1/1 Running 1 6m52s
healthcheck-demo-745554966d-ghxqk 1/1 Running 0 6m46s
healthcheck-demo-745554966d-xwhp5 1/1 Running 0 6m49s